Soil nailing is a known technique of ground reinforcement for supporting the sides of a cut excavation. This technique involves the insertion into the ground, either in a preformed hole or by percussion, of a reinforcing element, usually a metal rod. Usually the reinforcing elements are grouted to ensure good contact with the ground.
U.S. Pat. No. 3,802,204 is representative of one known method of soil nailing. This patent discloses an array of rows and columns of dowels extending into the cut embankment. The dowels are formed by filling bore holes extending through the skin of the cut face with cement grout and inserting a reinforcing rod into the bore hole before the grout sets. An end portion of the reinforcing rod extends outwardly from the bore hole, beyond the face of the embankment, which allows the dowel to be secured to a beam, effectively tying the entire structure together. A bearing plate may be fitted over the projecting end of the reinforcement rods and fastened, so as to pull the bearing plate against the beam. An outer layer of pneumatically applied concrete, such as shotcrete, typically 4 inches thick, is sprayed over the assembly to complete the retaining structure. The soil reinforcement system does not use precast facing panels. Moreover, the outer layer concrete facing has limited durability and does not present a pleasing appearance.
Soil reinforcement systems using precast concrete facing panels also are known in the art. For example, U.S. Pat. No. 4,449,857 discloses a backfill wall-type soil retaining system. In a backfill wall-type system, the wall is built from the bottom up. The panels are set in place, starting with the bottommost panel. After the panels are set, flexible reinforcements are fixed to the back side of the panels and are then covered with compacted soil, thus raising the soil elevation behind the panels. As each row of panels is added, the process is repeated. The connection system for the wall system disclosed in U.S. Pat. No. 4,449,857 includes a U-shaped anchoring member, which is preferably embedded in the facing panel. Each facing panel is preferably connected to two sets of soil reinforcing wires, although more or less may be employed. Since the reinforcing wires can be placed in the backfill behind the wall at their desired locations, the connection system is not designed to accommodate significant misalignments of the reinforcing wires.
A cut wall-type system, as disclosed and claimed herein, is fundamentally different in construction than a backfill wall-type system. For example, in a cut wall-type system, reinforcements are inserted as the excavation is made, from the top down. In a cut wall-type the panels are erected from the bottom up, similar to a backfill wall-type, but the type of reinforcements and the type of connection system are significantly different. The cut wall-type, as disclosed and claimed herein, has a connection system that can accommodate significant misalignment of the reinforcements. Misalignment must be anticipated since the reinforcements are placed from the top down as the excavation is made. The wall system disclosed and claimed herein does not require the reinforcements to be connected to every panel as does the backfill wall-type disclosed in U.S. Pat. No. 4,449,857. In addition the types of reinforcements disclosed in U.S. Pat. No. 4,449,857 cannot be installed in a natural ground deposit behind a cut.
It is also known to use a soil reinforcement system comprising precast facing panels fixed to soil nails. This known system also has the significant difficulty of aligning the soil nails with their connectors on the facing panels.